Optical beam couplers have a wide variety of applications throughout scientific, industrial, medical, and military fields. For example, pump and signal beams of different wavelengths frequently must be launched into waveguide amplifier media (e.g., a planar-waveguide (PWG) or an optical fiber) simultaneously. All-glass pump couplers, in which the pump input, signal input, and amplifier waveguides, are spliced or fused together, are efficient and robust when employed. However, all-glass pump couplers are not always feasible. For example, all-glass pump couplers may not be used between fiber inputs and PWGs of dissimilar materials. In such cases, the pump & signal inputs must be coupled into the amplifier waveguide via free space components. Conventional methods and systems for free-space coupling pump beams and seed signals into a fiber or planar-waveguide amplifier require one or more dichroic mirrors. This is problematic when the pump beam is unpolarized, such as when the pump beam is generated from a fiber-coupled diode laser module. This makes the dichroic mirror coating design challenging or, alternatively, requires keeping the incident pump at near-normal incidence on the dichroic mirror. The latter is generally accomplished by adding additional turning mirrors for the pump beam, which proportionately increase the size and weight of the coupling assembly. Additionally, mirror alignments are sensitive to shock, vibration, and changes in ambient temperature.